Skid-Steer Drive Layout With Nested Cross-Shaft and Differential
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Solution Overview
Problem
Existing drive configurations for skid steered vehicles, particularly those using cross-shaft electric drive systems, face challenges related to packaging efficiency, maintenance complexity, and the need for oversized motors and power converters due to regenerative steering power handling.
Innovation Solution
A drive unit configuration that includes a controlled differential connected between two shafts, with at least one steer motor and one electric propulsion motor, and a gear reduction/unit positioned between the controlled differential and the electric propulsion motor, allowing for a more efficient package and simplified maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a cross-shaft electric drive system is used with mechanical regenerative steering arrangement, then the drive system can transfer braking power from inner track to outer track, but the propulsion cross-shaft should be separate from the motor shaft which increases the diameter of motor bearings making high speed motor difficult to achieve
Solution Approach 1:
The patent places the propulsion cross-shaft inside the hollow motor shaft, creating a nested configuration where the cross-shaft is contained within the motor shaft. This allows the cross-shaft to be positioned centrally without increasing the overall diameter of the motor assembly, enabling high-speed motor operation while maintaining mechanical regenerative steering power transfer capability.
Solution Approach 2:
The patent transitions from a side-by-side arrangement of motor shaft and cross-shaft to a concentric arrangement, utilizing the radial dimension efficiently. By positioning the cross-shaft within the hollow interior of the motor shaft, the design optimizes space utilization and avoids increasing the external diameter, thus enabling high-speed motor operation.
2Device complexity
If the propulsion cross-shaft is mounted outside of the motor or the motor is mounted outside of the propulsion shaft, then the arrangement can be simplified, but this increases the package size and adds need for idler gears, increasing the complexity of the arrangement and reducing its efficiency
Solution Approach 1:
The patent merges the motor shaft and propulsion cross-shaft into a single integrated assembly where the cross-shaft is positioned within the hollow motor shaft. This consolidation eliminates the need for separate mounting structures and idler gears, reducing the number of components and minimizing energy losses associated with additional gear interfaces, thereby improving drive efficiency.
3Adaptability or versatility
If a gear change is to be used in the cross-shaft electric drive system, then the propulsion cross-shaft should be separate from the motor shaft, but this increases the diameter of the motor bearings making a high speed motor difficult to achieve
Solution Approach 1:
The patent implements the gear change mechanism within the hollow interior of the motor shaft, nesting the gear components inside the existing motor shaft structure. This approach allows gear change capability to be added without increasing the external diameter of the motor bearings, maintaining high-speed motor performance while providing adaptability for different operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances packaging efficiency and simplifies maintenance by locating all gearing systems together, while also allowing for smaller electric propulsion motors by mechanically transferring steering power, thus reducing the overall size and complexity of the drive system.
Implementation Method 1
a controlled differential positioned between and connecting two shafts and being in driveable communication with each shaft
Implementation Method 2
at least one steer motor in driveable communication with the controlled differential
Implementation Method 3
at least one electric propulsion motor in driveable communication with the drive unit outputs
Implementation Method 4
a gear reduction unit and/or a gear change unit positioned between the controlled differential and the at least one electric propulsion motor
Data Source
AI summary
A drive unit for a skid steered vehicle includes a controlled differential positioned between two shafts. The end of each shaft forms an output of the drive unit connected directly to the differential outputs via the shafts. A steer motor is in driveable communication with the differential, and an electric propulsion motor is in driveable communication with the shaft outputs. A gear reduction unit, and optional gear change unit, is positioned between the differential and the electric propulsion motor. The electric propulsion motor, the gear reduction unit and optional gear change unit are connected in a parallel connection with an output of the differential to the shaft outputs. The optional gear change unit includes an epicyclic gear reduction unit having an input and an output which provides drive input from the gear change unit to the shaft. A gear change set has a master gear that receives drive output from the electric propulsion motor, and slave gears which are driven by the master gear via one or more gear chains. A dog clutch slideably engages the input of the gear reduction unit and selectively engages with the master gear or slave gears so that the selected position of the dog clutch determines which gear is engaged.